Installations

From the German alps to the Canary Islands, the Israeli desert and India, researchers at Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany, are investigating the ageing of solar thermal collectors by learning more about the specific loads for different materials and components under extreme climate conditions.

Initial results show that the loads are very different, depending on geographic location and that the exposed collectors are of very high quality. Re-measuring collector performance after one year has shown no significant changes. The newfound knowledge will be used to establish adequate accelerated ageing test sequences for collectors and components (absorbers, reflectors, glazing, insulation) and to develop service life prediction models. Ultimately, the findings could lead to optimised collector designs and better materials for specific applications and installation sites.

Drawing from his expertise in performing comprehensive R&D investigations at an early development stage, Karl-Anders Weiß, head of the group Service Life Analysis at Fraunhofer ISE, explains why this work specifically focuses on solar thermal collectors: “Solar thermal collectors are the components that have to withstand the most demanding conditions in solar thermal systems, such as humidity, UV irradiation, very high temperatures, fast temperature changes, etc.”

Based on these initial findings, Weiß proposes that solar technology developers should optimise collectors and the choice of materials for the specific climatic and operational conditions or the site where a system will be installed. This is why the tests on Gran Canaria, one of the Spanish Canary Islands, was particularly significant. “On Gran Canaria, we have very harsh climate with high corrosive atmosphere due to salty air, combined with high winds and UV loads,” the expert explains.

The tests are part of SpeedColl, a 4-year cooperative project by Fraunhofer ISE and the University of Stuttgart’s Institute for Thermodynamics and Thermal Engineering (ITW) project aimed at analysing the ageing processes and the development of accelerated ageing tests for solar thermal collectors and their components. Test systems are installed on Germany’s highest mountain, the Zugspitze, in Freiburg and Stuttgart in Southern Germany, on Gran Canaria, in Israel’s Negev Desert and in India.